Objective: To evaluate olanzapine as a cluster headache abortive agent in an open-label trial.

Background: Cluster headache is the most painful headache syndrome known. There are very few recognized abortive therapies for cluster headache and fewer for patients who have contraindications to vasoconstrictive drugs.

Methods: Olanzapine was given as an abortive agent to five patients with cluster headache in an open-label trial. The initial olanzapine dose was 5 mg., and the dose was increased to 10 mg. if there was no pain relief. The dosage was decreased to 2.5 mg. if the 5 mg. dose was effective but caused adverse effects. To be included in the study, each patient had to treat at least two attacks with either an effective dose or the highest tolerated dose.

Results: Five patients completed the investigation (four men, one woman; four with chronic cluster, one with episodic cluster). Olanzapine reduced cluster pain by at least 80 percent in 4 of 5 patients, and two patients became headache-free after taking the drug. Olanzapine typically alleviated pain within 20 minutes after oral dosing and treatment response was consistent across multiple-treated attacks. The only adverse event was sleepiness.

Conclusions: Olanzapine appears to be a good abortive agent for cluster headache. It alleviates pain quickly and has a consistent response across multiple treated attacks. It appears to work in both episodic and chronic cluster headache.